Tone-arm for sound-reproducing machines



A. R. RASTALL.

TONE ARM FOR SOUND REPRODUCING MACHINES.

APPLICATION FILED FEB. 6, 1920. Y 1,400,983, Patented D60. 20, 1921.

2 SHEETSSHEET l.

A. R. RASTALL.

TONE ARM FOB souNn R'EPRODUCING MACHINES.

APPLICATION FlLED FEB.'6,1920.

Patented Dec. 20, 1921.

2 SHEETS-SHEET 2- UNITED STATES ARTHUR ROBERT RASTALL, OF EALING, ENGLAND.

TONE-ARM FOR SOUND-REPRODUCING MACHINES.

Specification of Letters Patent.

Patented Dec. 20, 1921.

Application filed February 6, 1320. Serial No. 356,591.,

To all whom it may concern Be it known that I, ARTHUR ROBERT RAs'rALL, a subject of the King of Great Britain, residing at 21 Ranelagh road, Ealing,MiddleseX, England, have invented a new and useful Improved Tone-Arm for Sound-Reproducing Machines, of which the following is a specification.

My invention relates to an improved sound-arm or tone-arm for gramophones, phonographs and like sound reproducing machines.

As is well known tone-arms or sound-arms have heretofore usually been made ofmetal. It has, however, been proposed to make them of wood and my invention has for its object an improved wood tone-arm and means for producing the same.

According to the invention I construct a tone-arm of a central taper sectionformed of a single-piece of wood which is bored throughout its length to the requisite diameter and a pair of radial or knee-shaped bends secured to either end of the said taper section. Each of these terminal bends is formed from a single block of wood and is bored so as to provide a curved duct or passage which is continuous with that of the taper section of the arm and is free from .angles so that when the three parts are assembled the duct or passage through the same is continuous and entirely free from ob 'ectionable angles.

0 produce the bends I advantageously proceed as follows, that is to say, I provide a block of wood of the shape of a quarter of a disk and I mount the said block in an appliance which is fitted to a lathe bed, and which comprises a support or base to which is pivoted an arm in which the block is clamped so that one of its faces can be presented to a boring bit secured in the lathe 1 chuck. It, now, the drill be rotated and the arm turned so as gradually to advance the block against the latter, a curved hole is bored in the wood. This is continued until the tool has bored half way through the wood block when the latter is removed, reversed, and the boring continued from the other end of the block. When four blocks have thus been bored' they are connected together by four plugs and are then turned externally in the ordinary way so as to produce four finished bends.

To enable the invention to be fully underthroughout the length of the section.

stood I will describe it by reference to the accompanying drawing, in which Figure l is a sectional elevation of one type of tone-arm made according to the invention.

Fig. 2 is a plan view thereof.

Fig. 3 is a perspective view of one of the quadrantal blocks from which a terminal bend is made.

Figgl is an elevation of the clamp or holder for boring the wood blocks.

Fig. 5 is a plan view thereof, and

Fig. 6 is a sectional view showing the method of fitting the four blocks together for externally shaping them by turning.

a indicates the taper section of the tonearm which, as above described, is or wood and is bored with a taper duct or passage so as to leave walls of uniform thickness 1; is one terminal bend and c the other bend, these two bends being connected to the two extremities of the taper section a so that they lie in place at right angles to one another, and each of them being bored with a duct or passage which is without any sharp angles and is continuous in each case with that of the taper section a.

Fig. 3 shows one of the blocks of from which a terminal bend is made. This block, as shown, is of the shape of a quarter of 'an annulus. Figs. 4c and 5 show the holder or clamp securing the block (Z to the lathe-bed for the purpose of boring the passage or duct in the same. This appliance comprises the support or base which is fitted to the lathe bed A in the usual way and the arm 9 is pivotally mounted on the upright pin it on the base-piece f and is provided with the recess a of the shape to receive the curved block (Z which is secured in position by means of the clamping plate 7'. The arm 9 is also furnished with the handle 70 by means of which it can be turned.

When the block (Z is securely fixed in position, the appliance is clamped adjacent to a drill-bit, such as Z which is secured to the lathe-chuck in the ordinary way. It, now, the said drill be rotated and the holder arm 9 moved in the direction of the arrow, Fig. 5, a curved hole, duct or passage is bored in the block (Z. When the drill has bored half the length ot' the passage as indicated by the dotted lines, the block (Z is removed from the holder, reversed in position and the bor ing completed from the other end or face so as to produce the complete passage.

When four such bends have been bored they are placed together in the manner indicated in Fig. 6 and secured by the wood plugs m. They are then chucked in a lathe and shaped externally so as to produce four finished bends.

The tone-arm is attached to the machine in any convenient way and preferably by means of the construction shown in Figs. 1 and 2, that is to say, the end of the bendb is furnished with a vulcanite or metal ring a through which pass pins 0, the ends of 15 which project externally from the ring a and engage with a peripheral groove p in a vulcanite or metal ring 9 fitted into a recess in the top of the ring '1". This construction permits of the necessary movements of the tonearm.-

Claim:

A method of making a plurality of hollow wooden tone arm elbows, which consists in forming each of a plurality of blocks in the shape of a fraction of an annulus, boring a curved passage through each of said blocks having the same diameter throughout, securing the blocks together to form an annulus and shaping the exterior of said annulus.

ARTHUR ROBERT RASTALL. 

